drm/i915/gsc: GSC firmware loading

GSC FW is loaded by submitting a dedicated command via the GSC engine.
The memory area used for loading the FW is then re-purposed as local
memory for the GSC itself, so we use a separate allocation instead of
using the one where we keep the firmware stored for reload.

The GSC is not reset as part of GT reset, so we only need to load it on
first boot and S3/S4 exit.

v2: use REG_* for register fields definitions (Rodrigo), move to WQ
    immediately

v3: mark worker function as static

Bspec: 63347, 65346
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Alan Previn <alan.previn.teres.alexis@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221208200521.2928378-4-daniele.ceraolospurio@intel.com

drivers/gpu/drm/i915/gt/intel_gpu_commands.h

@@ -21,6 +21,7 @@
 #define INSTR_CLIENT_SHIFT      29
 #define   INSTR_MI_CLIENT       0x0
 #define   INSTR_BC_CLIENT       0x2
+#define   INSTR_GSC_CLIENT      0x2 /* MTL+ */
 #define   INSTR_RC_CLIENT       0x3
 #define INSTR_SUBCLIENT_SHIFT   27
 #define INSTR_SUBCLIENT_MASK    0x18000000
@@ -432,6 +433,12 @@
 #define COLOR_BLT     ((0x2<<29)|(0x40<<22))
 #define SRC_COPY_BLT  ((0x2<<29)|(0x43<<22))
 
+#define GSC_INSTR(opcode, data, flags) \
+	(__INSTR(INSTR_GSC_CLIENT) | (opcode) << 22 | (data) << 9 | (flags))
+
+#define GSC_FW_LOAD GSC_INSTR(1, 0, 2)
+#define   HECI1_FW_LIMIT_VALID (1 << 31)
+
 /*
  * Used to convert any address to canonical form.
  * Starting from gen8, some commands (e.g. STATE_BASE_ADDRESS,